/Engine/Source/Runtime/AnimationCore/Public/BoneWeights.h
Set a new bone weight. If an existing weight exists with the same bone index, it's weight value is replaced with the weight value of the given entry. Otherwise a new index is added. In both cases the new entry is subject to the given settings, which may influence what the entry's final weight value is and whether it gets thrown away for not passing the threshold value. If the weight was successfully incorporated, then this function returns true. Otherwise it returns false.
bool SetBoneWeight ( [FBoneWeight](API\Runtime\AnimationCore\FBoneWeight) InBoneWeight, const [FBoneWeightsSettings](API\Runtime\AnimationCore\FBoneWeightsSettings) & InSettings )